Dryland Systems Yields over 24 Years As Impacted By Potential ET Site and Soil Landscape Position.

No-till management in the Central Great Plains has allowed for more diversified cropping systems with both spring and fall planted crops.  This shift reduces the time systems are in summer fallow.  The success or failure of a dryland cropping system in this semi-arid region often depends on the timing and amount of precipitation.  Our research over environmental factors of potential ET (PET) and soil types along a catena landscape has focused on diversity of the cropping system.  This study has allowed for the evaluation of systems during above to average precipitation years to predominately drought years.  The 1^st 12 years of the study were predominately above average rainfall (wet years) whereas the 2^nd 12 year period was in moderate to severe drought (dry years).  Annualized cropping system yields during the wet years showed that as cropping intensity increased so did the yields with the highest on the toeslope landscape across all 3 PET sites.  Average annualized cropping system yields during the dry years (13-24 years) showed yields on toeslopes were higher but cropping system had less impact.  This is due to a change in rotations after the 1^st phase whereby wheat (Triticum aestivum)-fallow (WF) and wheat corn (Zea mays L.)-millet (Panicum miliaceum)-fallow (WCMF) were replaced by WCM and WWCM systems.  This resulted in only one system that had a summer fallow phase.  Averaged over soils in the dry years at each PET site, annualized yields were similar across all rotations with the highest yields found in the CC system, which also had the highest variability.  Comparisons of wet and dry years averaged over soils, indicated that all rotations had higher average annualized yields compared to the WF system at all PET locations.  This was also true when averaged over sites and seeing the impact of landscape position (soils).